At 9G, your blood weighs nine times what it normally does. Your arms feel like they are filled with wet cement. Your vision collapses from the edges inward until you are looking through a drinking straw. And if you do not fight it — actively, violently, every three seconds — you will be unconscious in about five seconds.

This is what happens inside your body when a fighter jet turns hard.

The Progression: From Color to Black

Under positive G-forces — the kind you feel in a hard pull-up or sustained turn — blood drains from your head to your feet. The sequence that follows is well-documented and mercilessly predictable:

Tunnel vision comes first. Your peripheral vision narrows progressively, as though someone is closing curtains from both sides. Then grey-out: color drains from the world, leaving everything monochromatic and hazy. Next is blackout — complete loss of vision, though you may briefly remain conscious. Finally comes G-LOC (G-force induced Loss of Consciousness): the brain loses blood supply entirely and you pass out.

An untrained person typically blacks out between 4 and 6G. If the G-onset is rapid — more than 1G per second — G-LOC can occur without any visual warning at all. You go from normal to unconscious with no tunnel vision, no grey-out, nothing. Average incapacitation during G-LOC lasts about 12 seconds, followed by several seconds of disorientation.

In a fighter jet traveling at 500 knots, 12 seconds covers about three miles.

How Pilots Fight Back

Fighter pilots use two defenses against G-forces: hardware and technique.

The G-suit contains inflatable bladders over the calves, thighs, and abdomen. Under high G-loads, the bladders automatically inflate with compressed air, squeezing blood vessels and forcing blood back toward the heart and brain. A G-suit adds roughly 1G of protection.

The real weapon is the Anti-G Straining Maneuver (AGSM) — a combination of forced breathing against a closed throat every three seconds and intense contraction of leg, abdominal, and back muscles to prevent blood pooling in the lower body. A properly executed AGSM adds approximately 4G of protection. The math works out neatly: baseline tolerance (4.5G) + G-suit (+1G) + AGSM (+4G) = roughly 9G.

Pilots train until the AGSM is automatic, because poor timing actually makes things worse. A 1982 U.S. Air Force study showed that weight training increases G tolerance by 10-15%.

The Man Who Survived 46G

On December 10, 1954, Dr. John Paul Stapp rode the Sonic Wind I rocket sled at Holloman Air Force Base to 632 mph in 5 seconds, then stopped in just 1.4 seconds. The deceleration hit 46.2G. For the briefest moment, his 168-pound body weighed approximately 6,800 pounds.

He cracked ribs, broke both wrists, and was temporarily blinded when the G-forces burst every blood vessel in his eyes. His research proved that properly restrained pilots could survive crashes at forces previously assumed to be fatal — and led directly to mandatory seatbelts in automobiles.

What the Jets Can Handle

Different fighters have different structural limits. The F-16 and MiG-29 are rated for +9G. The F/A-18 Hornet caps at +7.5G. The L-39 Albatros handles +8G. The F-35A matches the F-16 at 9G, though the B and C carrier/STOVL variants are limited to 7-7.5G.

Then there is the other direction. Negative G — pushing the nose over or flying inverted — sends blood rushing to the head instead of away from it. This causes red-out: vision takes on a reddish tint as blood floods the eye vessels. Red-out can occur at as little as -2 to -3G, and sustained negative G can cause retinal damage and hemorrhagic stroke. G-suits provide zero protection against negative G. The human body tolerates far less of it.

What You Will Feel on a MiGFlug Flight

Passengers on MiGFlug flights typically experience 4G to 7G, depending on the aircraft and the maneuvers. At 4-5G, most passengers feel the edges of their vision going grey. The G-suit inflates around your legs — a sudden, firm squeeze. Breathing becomes work; your chest feels like someone parked a concrete slab on it. The pilot pulls into loops, rolls, Immelmann turns, and split-S maneuvers.

For context: your average rollercoaster hits about 3-5G momentarily. The highest G-force on a currently operating rollercoaster is 5.5G on Shock Wave at Six Flags Over Texas.

A fighter jet sustains those forces for seconds at a time, not fractions of a second. That is the difference between a thrill ride and the real thing.

Sources: Federal Aviation Administration Aeromedical Library, USAF School of Aerospace Medicine, Aerospace Medical Association, Aviation Week